The present invention relates to a friction brake, in particular a disc brake, for a motor vehicle with a friction element, e.g. a brake disc, coupled to the rotation of a vehicle wheel and brake linings assigned to it which can be pressed against the friction element by a disc brake clamping device.
Due to high demands of said friction brakes with regard to the brake clamping force as well as the tension force dynamics, especially within modern controllable brake systems, usually high-performance brake clamping devices and related energy sources are necessary. Yet, the high-performance brake clamping devices and energy sources are not only expensive, but present also disadvantages with regard to their weight and their dimensions. Above all, this has a negative effect on such friction brakes that are provided with brake clamping devices being operated electrically, electromechanically or by an electric motor.
In DE 42 07 640 C2 a motor vehicle disc brake is disclosed in which a mechanical brake clamping device for pressing brake linings onto a respective brake disc acts upon at least one brake lining. In this case the brake disc is connected in an unrotatable manner with a vehicle wheel. The energy source for operating the clamping device is the rotating vehicle wheel itself respectively the brake disc coupled to the clamping device by means of a friction clutch. In order to actuate the brake, the friction clutch can be brought electromagnetically into frictional engagement with the brake disc thus taking up the rotational energy from the brake disc and introducing it into the clamping device. Therefore, toothed wheels between the friction clutch and the clamping device are provided causing a torque transmission respectively introduction into the clamping device of the friction brake. A conversion of the rotational movement into a translation movement to be transmitted to the brake lining is achieved within the clamping device by means of a ball and ramp arrangement. The ball and ramp arrangement, however, presents the disadvantage of having a limited clamping path, which may be insufficient in case of very worn-out brake linings. Using the rotational energy of the brake disc for clamping the brake during its actuation eliminates the need for an expensive high-performance driving source. The disadvantage of such an arrangement certainly is that very large components with a relatively high moment of inertia have to be put into rotation within the friction brake. Due to the direct frictional engagement with the brake disc, the friction clutch is also subject to the thermal influences of the brake disc that affect its function and may have a negative effect on the friction value within the friction clutch. Furthermore friction clutch and toothed wheels for the clamping device are exposed without protection to environmental influences, as e.g. dirt and humidity.
On this basis, it is the object of the present invention to indicate a generic friction brake that allows clamping the friction brake without an expensive clamping device with energy source under any operating condition and overcomes the above-mentioned disadvantages of the state of the art.